Retrievable sensors are sensors which can be replaced while process fluids are present in the area in which the pressure is to be measured. Such pressure sensors are attached in the pipe wall by way of a flange or bore, for example. It is known to use valve mechanisms for blocking the flow to enable the replacement of the pressure sensor. In practice, the use of valves has proven to be difficult as they are left in an open position and subject to fouling by the process fluid. It is therefore a great risk that the valve is not operable when it is finally needed for the replacement of a pressure sensor, after some 10-15 years, for example. Moreover, when valves are used it is difficult to avoid discharge of process fluid into the environment.
It is therefore a need for a pressure sensor having a reliable structure making it possible to replace pressure sensors in overpressure environments in a simple manner without rendering the pressure sensors inoperable and without having to open up the pipe wall or suspend the production/process. At the same time, the pressure sensor has to meet strict safety requirements.